Organic red electroluminescent chromophores, method for the production and use thereof

ABSTRACT

The invention relates to chromophores exhibiting semiconductive properties, the production and use thereof as luminophores in organic light-emitting diodes (OLEDs) and organic solar cells. The invention more specifically relates to highly condensed boron complex compounds wherein the boron atoms have improved processability, solubility and the fluorescence quantum efficiency is increased by building up by spirocenters.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the 35 USC 371 National Stage of International ApplicationPCT/DE02/00550 filed on Feb. 15, 2002, which designated the UnitedStates of America.

FIELD OF THE INVENTION

The invention relates to chromophores with semiconducting properties,their production and use as luminophores in organic light emittingdiodes (OLEDS) and organic solar cells.

BACKGROUND OF THE INVENTION

In patent applications DE 10002423 and DE 10002424 as well as inapplications DE 10038436 and DE 10038437 (all hitherto unpublished), neworganic semiconductor materials have already been presented whichexhibit high fluorescence and form glaseous phases also as solids.

The new semiconductor materials are suitable for covering thelong-wavelength emitting spectral range (orange to red) and belong tothe “small molecules”, although they can also be processed by spincoating. The materials are suitable both for the construction of organiclight emitting diodes (OLEDs) and for the construction of organicphotovoltaic elements and finally also for the construction of otherorganic electronic devices, these being able to be used in both hole andelectron transfer layers and in emitter layers.

The materials are preparatively accessible in high yields and areobtained from 2-N,N-di(het)aryl aminothiophene and/or -thiazolederivatives.

There is additionally a need for new organic semiconducting and/oremitting materials for a wide range of applications in organic devicesand light emitting diodes.

The new materials according to the invention extend the range ofintensively luminescent, boron complex based compounds claimed inapplication GR 200102309.

SUMMARY OF THE INVENTION

The object of invention is to create new, organic, thermally andphotochemically stable, long-wavelength emitting electroluminescentcompounds which can be used in light-emitting diodes and/or organicelectronic devices, which are easily accessible preparatively and whichlend themselves to mass production processes.

The subject matter of the invention is a highly condensed, boron complexbased compound having the general structure I.

-   -   where R¹ and R², which can be the same or different        independently of one another, stand for hydrogen, halogen,        pseudohalogen, a nitrile and/or nitro group, an unsubstituted or        alkyl, aryl and hetaryl substituted —NR³R⁴, —OR⁵, —PR³R⁴ and        —SR⁶ and/or for a fused carbocyclic or heterocyclic ring, these        groups possibly being branched or unbranched, containing 1 to 20        C atoms and containing various functional groups with N, O, S        and/or P atoms in the event that R³ to R⁶ is alkyl;    -   where X¹ and X², which can be the same or different        independently of one another, stand for halogen, preferably        fluorine, alkyl- or aryloxy, the alkyl groupings possibly being        branched or unbranched    -   and containing 1 to 20 C atoms and various functional groups        with N, O, S and/or P atoms or    -   both jointly forming a cycle with the boron atom through an at        least bidentate ligand, the at least bidentate ligand possibly        having hydroxy and/or carboxylic acid groups and being        preferably a diol, a hydroxy carboxylic acid or a dicarboxylic        acid such as —OC₂H₄O—, —OC₃H₆O—, glycolate, lactate, tartrate,        sylicylate, mandelate, benzilate, 1,2- or 2,3-hydroxynaphthoate,        oxalate, malonate, alkylmalonate or dialkymalonate.

In the new long-wavelength emitting luminophores according to theinvention, the tendency to crystallize is suppressed by the additionalintroduction of spiro elements so that the resultingthree-dimensionality of the chromophores prevents or limits the stackingof the molecules to form crystals.

In the boron complex based compounds, the boron atoms act as spirocenters, promote the formation of glaseous phases of the system andprevent unwanted crystallization which causes a reduction in thesystem's fluorescent properties. The positive characteristics of spirocenters in organic semiconducting materials are already known.

Reaction scheme:

The highly condensed, boron complex based type I compounds according tothe invention are produced from the type II compounds described in theliterature (K. Kitahara, H. Nishi, J. Heterocyclic Chem. 25 (1988)1063), in which the groups R¹ and R² as well as X¹ and X² have theabovementioned meanings, according to methods known in themselves, bytheir reaction with suitable boron compounds, possibly in the presenceof a suitable coreagent and in the presence of a suitable solvent atelevated temperatures.

In particular, boron esters of carboxylic acids, preferably di- oroligocarboxylic acids and/or hydroxy-substituted carboxylic acids andcomplex adducts of boron halogenides with electron-donating solventshave been found to be suitable boron compounds for reacting with II.

Because of their high thermal and photochemical stability and theirhigh-vacuum evaporability without decomposition at elevated temperaturesas well as their ability to electroluminesce, the novel boron-complexedtetraaryl-diazaperylene heterocycles of type I are advantageouslysuitable as emitter materials for producing organic light-emittingdiodes (OLEDs) and as a photochemically stable, photoactive material inorganic solar cells and/or in other organic electronic devices. Thermaldecomposition of these materials takes place only at temperatures >470°C.

DETAILED DESCRIPTION OF THE INVENTION

The following examples are intended to explain the invention in greaterdetail. Examples 1 to 3 describe the type II synthons required forproducing the highly condensed, boron complex based type I compoundsaccording to the invention. Examples 4-8 describe the production of theboron-complexed, highly condensed heterocycles from class Itetraaryl-diazaperylenes.

EXAMPLE 1

Synthesis of Diazaperylene Type II/1 R¹=R²=H

0.1 mol of 2-amino benzophenone III and 0.05 mol of succinylosuccinicacid diethyl ester IV are refluxed for 5 h in 50 ml of ethanol and 1 mlof hydrochloric acid. The product IIa precipitated from the reactionsolution after cooling with a yield of 70% is drawn off, dried and thenrefluxed in 25 ml of 1-chloronaphthalene for 30 minutes. After cooling,the resulting product II/1 is isolated by suction and washed withapproximately 200 ml of methanol for cleaning. Yield 70%; mp 405° C. Theproduct has an absorption maximum of 648 nm and an emission maximum of704 nm in ortho-dichlorobenzene.

EXAMPLE 2

Synthesis of Diazaperylene Type II/2 R¹=Cl R²=H

Similarly to Example 1, 0.1 mol of 2-amino-5-chlorobenzophenone III and0.05 mol of succinylosuccinic acid diethyl ester IV are reacted in 50 mlof ethanol and 1 ml of hydrochloric acid. The product IIa precipitatedfrom the reaction solution after cooling is drawn off, dried and thenrefluxed in 25 ml of 1-chloronaphthalene for 30 minutes. After cooling,the resulting product II/2 is isolated by suction and washed withapproximately 200 ml of methanol for cleaning. Yield 82%; mp 470° C. Theproduct has an absorption maximum of 649 nm and an emission maximum of706 nm in o-dichlorobenzene.

EXAMPLE 3

Synthesis of Diazaperylene Type II/3 R¹=R²=Cl

Similarly to Example 1, 0.1 mol of 2-amino-2′,5-dichlorobenzophenone IIIand 0.05 mol of succinylosuccinic acid diethyl ester IV are reacted in50 ml of ethanol and 1 ml of hydrochloric acid. The product IIaprecipitated from the reaction solution after cooling is drawn off,dried and then refluxed in 25 ml of 1-chloronaphthalene for 30 minutes.After cooling, the resulting product II/3 is isolated by suction andwashed with approximately 200 ml of methanol for cleaning. Yield 85%;mp>360° C. The product has an absorption maximum of 656 nm and anemission maximum of 708 nm in o-dichlorobenzene.

EXAMPLE 4

Synthesis of Boron-Complexed Diazaperylene Type I/1 R¹=R²=H;X¹=X²=—O—CO—CH₃

To a solution of boron acetate in an acetic acid/acetic anhydridemixture produced by dissolving 10 g of boric acid in 250 ml of aceticanhydride are added 0.05 mol of the starting compound II/1. This isrefluxed until a virtually clear solution is obtained. After hotfiltration it is allowed to cool and the resulting product I/1 isisolated by suction. Yield 95%; mp 380° C. The product has an absorptionmaximum of 567 nm and an emission maximum of 613 nm in acetone.

EXAMPLE 5

Synthesis of Boron-Complexed Diazaperylene Type I/2 R¹=Cl, R²=H;X¹=X²=—O—CO—CH₃

To a solution of boron acetate in an acetic acid/acetic anhydridemixture produced by dissolving 10 g of boric acid in 250 ml of aceticanhydride are added 0.05 mol of the starting compound II/2. This isrefluxed until a virtually clear solution is obtained. After hotfiltration it is allowed to cool and the resulting product I/2 isisolated by suction. Yield 92%; mp 379° C. The product has an absorptionmaximum of 581 nm and an emission maximum of 630 nm in acetone.

EXAMPLE 6

Synthesis of Boron-Complexed Diazaperylene Type I/3 R¹=Cl, R²=H;X¹=X²=—O—CO—C₅H₁₁

To a solution of boron capronate in a caproic acid/caproic anhydridemixture produced by dissolving 10 g of boric acid in 250 ml of caproicanhydride are added 0.05 mol of the starting compound II/2. This isrefluxed until a virtually clear solution is obtained. After hotfiltration it is allowed to cool and the resulting product I/3 isisolated by suction. Yield 90%; mp>360° C. The product has an absorptionmaximum of 582 nm and an emission maximum of 630 nm in acetone.

EXAMPLE 7

Synthesis of Boron-Complexed Diazaperylene Type I/4 R¹=Cl, R²=H;X¹=X²=—O—CO—C₃H₇

To a solution of boron butyrate in a butyric acid/butyric anhydridemixture produced by dissolving 10 g of boric acid in 250 ml of butyricanhydride are added 0.05 mol of the starting compound II/2. This isrefluxed until a virtually clear solution is obtained. After hotfiltration it is allowed to cool and the resulting product I/4 isisolated by suction. Yield 85%; mp>360° C. The product has an absorptionmaximum of 582 nm and an emission maximum of 630 nm in acetone.

EXAMPLE 8

Synthesis of Boron-Complexed Diazaperylene Type I/5 R¹=R²=Cl;X¹=X²=—O—CO—CH₃

To a solution of boron acetate in an acetic acid/acetic anhydridemixture produced by dissolving 10 g of boric acid in 250 ml of aceticanhydride are added 0.05 mol of the starting compound II/3. This isrefluxed until a virtually clear solution is obtained. After hotfiltration it is allowed to cool and the resulting product I/5 isisolated by suction. Yield 82%; mp>360° C. The product has an absorptionmaximum of 573 nm and an emission maximum of 620 nm in acetone.

1. A compound of formula I,

wherein R¹ and R², which can be the same or different independently ofone another, stand for one of hydrogen; halogen; pseudohalogen; anitrile and/or nitro group; an unsubstituted —NR³R⁴, —OR⁵, —PR³R⁴ and—SR⁶; —NR³R⁴, —OR⁵, —PR³R⁴ or —SR⁶ substituted with an alkyl, aryl, oran hetaryl; or R¹ and R² can be a fused carbocyclic or heterocyclicring; wherein X¹ and X², which can be the same or differentindependently of one another, stand for one of halogen, alkyl- andaryloxy, or both jointly forming a cycle with the boron atom through anat least bidentate ligand, the bidentate ligand having at least twoplaces to bind a central atom, the ligand having hydroxy and/orcarboxylic acid groups and being a diol, a hydroxy carboxylic acid or adicarboxylic acid that is one of —OC₂H₄O—, —OC₃H₆O—, glycolate, lactate,tartrate, sylicylate, mandelate, benzilate, 1,2- or2,3-hydroxynaphthoate, oxalate, malonate, alkylmalonate ordialkymalonate.
 2. A method for preparing the compound according toclaim 1, comprising reacting diazaperylene II with a compound selectedfrom the group consisting of at least one boron ester of either acarboxycyclic acid or a di- or oligocarboxylic acid or a di- oroligocarboxycylic acid or a hydroxy substituted carboxylic acid and acomplex adduct of a born halogenide to obtain the compound according toclaim
 1. 3. The method according to claim 2, wherein the reaction takesplace in at least one electron-donating solvent.
 4. A method ofpreparing an organic light-emitting diode, which comprises adding acompound according to claim 1 as an organic semiconducting emittermaterial in a hole and/or electron transfer layer of said organiclight-emitting diode (OLED).
 5. A method of preparing an organicelectronic device, which comprises adding compound I according to claim1 as an organic semiconducting material in said organic electronicdevice.
 6. A method of producing an organic solar cell, which comprisesadding compound I according to claim 1 as a photochemically stable,photoactive material in said organic solar cell.